Composites of N,N′-bis-(pyridyl) urea-dicarboxylic acid as new hydrogelators -: a crystal engineering approach

Sixteen composites of a hydrogelator N,N'-bis(4-pyridyl) urea 1 and a nongelator N,N'-bis(3-pyridyl) urea 2 with a series of dicarboxylic acids having various backbones have been prepared and characterized. Seven such composites-three from the composites of 1 and four from the composites of 2-turned out to be good to moderate gelling agents for pure water. Single crystal X-ray structures of three such gelators and four nongelators indicate that microporosity in the crystalline solid state structure may be one of the important criteria for hydrogelation. (c) 2007 Elsevier Ltd. All rights reserved.